1. Field of the Invention
Embodiments of the present invention generally relate to a device and a method of using the device where a plurality of smaller micro-electromechanical system (MEMS) devices replace a single, larger MEMS device.
2. Description of the Related Art
MEMS devices are routinely produced using semiconductor processing. This allows accelerometers, pressure sensors, low resistance current switches or RF switches, variable capacitance devices, resonators and other devices to be manufactured cheaply. For many of these devices to work with the desired physical properties they usually cover an area of several hundred microns square. It is then very difficult to seal such a device in a cavity using the typical interlayer dielectrics found in the back end or the metallization found in the back end because these are of the order of 1 micron thick. In many radio frequency applications, it is desirable to have a variable capacitor that can be used, for example, for tuning a resonant LRC circuit in an antenna module. The variable capacitor can be used for switching between carrier frequencies in a mobile phone or other apparatus that may be used at a number of different frequencies.
A low pressure cavity is usually required for the operation of these devices, which leads to a pressure on the roof of the cavity. With the MEMS devices being over 100 microns wide, the cavity will collapse under the external pressure. To solve this problem MEMS devices are separately packaged which can double the price of a device. In some applications it would be advantageous to have a MEMS device on the same chip as a micro controller or other logic device, but that is not possible because it must be separately packaged.
MEMS based accelerometers have been built using a variety of micro-machining techniques for many years. Most of these MEMS based accelerometers rely upon precise micro-machining of a single proof mass suspended by beams to set the sensitivity and signal range of the sensor. The typical sensing scheme is capacitance based, but other sensing strategies have been used. The size of the proof mass, is normally of the order of 100 microns in at least two dimensions, and may be a few microns in size in the third spatial dimension. Once the suspension system is added, careful packaging strategies ranging from reverse wafer bonding to full hermetic packages are required. These complex packaging strategies add to the cost of the sensor and limit the sensors ability to be fully integrated in a standard back and of the line (BEOL) or standard packaging flow.
Therefore, there is a need for a device integrated into the chip and a method for its manufacture.